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refactor: add overflow-safe CeilDiv helper

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Introduce `CeilDiv()` for integral ceiling division without the typical `(dividend + divisor - 1) / divisor` overflow, asserting a non-zero divisor.

Replace existing ceiling-division expressions with `CeilDiv()` to centralize the preconditions.

Add unit tests covering return type deduction, max-value behavior, and divisor checks.
This commit is contained in:
Lőrinc
2026-01-28 14:45:30 +01:00
parent 4a05825a3f
commit 02d047fd5b
15 changed files with 85 additions and 19 deletions
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37
src/test/util_tests.cpp
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@@ -1833,4 +1833,41 @@ BOOST_AUTO_TEST_CASE(mib_string_literal_test)
BOOST_CHECK_EXCEPTION(operator""_MiB(static_cast<unsigned long long>(max_mib) + 1), std::overflow_error, HasReason("MiB value too large for size_t byte conversion"));
}
BOOST_AUTO_TEST_CASE(ceil_div_test)
{
// Type combinations used by current CeilDiv callsites.
BOOST_CHECK((std::is_same_v<decltype(CeilDiv(uint32_t{0}, 8u)), uint32_t>));
BOOST_CHECK((std::is_same_v<decltype(CeilDiv(size_t{0}, 8u)), size_t>));
BOOST_CHECK((std::is_same_v<decltype(CeilDiv(unsigned{0}, size_t{1})), size_t>));
// `common/bloom.cpp` and `cuckoocache.h` patterns.
BOOST_CHECK_EQUAL(CeilDiv(uint32_t{3}, 2u), uint32_t{2});
BOOST_CHECK_EQUAL(CeilDiv(uint32_t{65}, 64u), uint32_t{2});
BOOST_CHECK_EQUAL(CeilDiv(uint32_t{9}, 8u), uint32_t{2});
// `key_io.cpp`, `rest.cpp`, `merkleblock.cpp`, `strencodings.cpp` patterns.
BOOST_CHECK_EQUAL(CeilDiv(size_t{9}, 8u), size_t{2});
BOOST_CHECK_EQUAL(CeilDiv(size_t{10}, 3u), size_t{4});
BOOST_CHECK_EQUAL(CeilDiv(size_t{11}, 5u), size_t{3});
BOOST_CHECK_EQUAL(CeilDiv(size_t{41} * 8, 5u), size_t{66});
// `flatfile.cpp` mixed unsigned/size_t pattern.
BOOST_CHECK_EQUAL(CeilDiv(unsigned{10}, size_t{4}), size_t{3});
// `util/feefrac.h` fast-path rounding-up pattern.
constexpr int64_t fee{12345};
constexpr int32_t at_size{67};
constexpr int32_t size{10};
BOOST_CHECK_EQUAL(CeilDiv(uint64_t(fee) * at_size, uint32_t(size)),
(uint64_t(fee) * at_size + uint32_t(size) - 1) / uint32_t(size));
// `bitset.h` template parameter pattern.
constexpr unsigned bits{129};
constexpr size_t digits{std::numeric_limits<size_t>::digits};
BOOST_CHECK_EQUAL(CeilDiv(bits, digits), (bits + digits - 1) / digits);
// `serialize.h` varint scratch-buffer pattern.
BOOST_CHECK_EQUAL(CeilDiv(sizeof(uint64_t) * 8, 7u), (sizeof(uint64_t) * 8 + 6) / 7);
}
BOOST_AUTO_TEST_SUITE_END()